For cooling the hot parts, especially the combustion chamber and the turbine through which flows the hot gas, gas turbines (gas turbine plants) typically use cooling fluids which are extracted from the compressor at a suitable pressure, sometimes recooled, and after cooling of the hot parts has been carried out are added to the turbine flow. In this case, the cooling of the thermally highly loaded components of a gas turbine is conventionally carried out according to a fixed scheme. In the simplest case, the cooling air proportion remains largely constant over wide operating ranges. This is also when a machine is operated in partial load operation with reduced hot gas temperatures, for example.
In order to vary and to control the volume of cooling air in proportion to the actual circumstances and to the operating conditions, EP 1028230 proposes to realize controlling of the material temperature of the cooled components by means of a variable cooling air supply. For this, it was proposed to equip thermally loaded components with thermoelements or other devices for temperature measurement. If the measured temperature exceeds a predetermined reference value, the volume of cooling air is increased. Vice versa, the cooling air is additionally restricted if the measured material temperature falls short of the predetermined reference value.
U.S. Pat. No. 6,615,574 deals with another problem. In order to realize a flexible supply with matching feed pressure, it is proposed to branch the compressed air from different stages of the compressor and to mix it in a controlled manner so that the volume of cooling air which is necessary for cooling is provided at an adequate feed pressure.
Furthermore, the use of a controllable secondary air system for increasing the hot gas temperature during partial load operation is known from EP1967717.
Specific adjustments of the cooling air flows for operation according to a predetermined operating concept are therefore known from the prior art. These, however, have little flexibility and do not allow any change of the operating concept as a function of operating targets.